A power supply device known in the related art includes a voltage stabilizer circuit that generates a reference voltage Vref from an input voltage Vin, and outputs the reference voltage Vref to a control circuit; and a voltage dropping circuit that generates a drive voltage Vcc by causing a voltage drop in the input voltage Vin, and outputting this drive voltage Vcc to a control circuit (See patent literature 1). This power supply device contains a storage unit including plural electrical double layer capacitors coupled in series. Moreover, by obtaining an input voltage Vin from the mutual contact point of the cathode of a diode coupled to the main power supply and a diode coupled to the storage unit, the higher voltage between the main power supply voltage Vb and storage unit voltage Vc that is voltage divided just by a voltage drop along the sequential (forward current) direction of the diodes can serve as an input voltage Vin. A correct input voltage Vin can in this way be continuously supplied to the control circuit by electrical power from the storage unit even if there is a sudden drop in the voltage Vb of the main power supply so that the control circuit can reliably stop operating without causing faulty operation.